1. Field of the Invention
This invention relates to a cosmetic and, more particularly, to a cosmetic having a high, long-lasting moisturizing effect.
2. Description of the Background
A normal horny layer of epidermis usually contains 10-20% of moisture which helps to impart elasticity, flexibility, or softness to the skin and to maintain a protective effect for the skin. It is known that when the moisture content decreases to less than 10% due to changes in environmental conditions or the like, this will cause the skin to lose its elasticity and protective function and develop a so-called dry-skin condition which causes various skin problems.
In order to avoid the dry-skin condition or to recover normal skin conditions, a hydrophilic humectant is included in the formulation of cosmetics. Hydrophilic humectants conventionally used are polyol compounds, such as polyethylene glycol, polypropylene glycol, dipropylene glycol, propylene glycol, and butylene glycol, glycerine, sorbitol, maltitol, amino acid, sodium pyrrolidone carboxylate, urea, lactic acid, hyaluronic acid, collagen, and the like.
However, these humectants are too hydrophilic to penetrate the horny layer of the normal skin. They usually remain on the surface of the epidermis, giving only an inadequate and temporary moisturizing effect to the skin.
In view of this situation the inventors have made extensive and earnest studies to obtain a cosmetic with a high and long-lasting moisturizing effect, and found that when both a diglyceride which is liquid at room temperature, and a polyol type humectant are included in the formulation of a cosmetic, they exhibit a moisturizing effect which is higher than when they are ued independently. In addition, it was found that the persistency of the effect can be synergetically enhanced. Such findings have led to the completion of this invention.